This invention relates to electromagnetic interference (xe2x80x9cEMIxe2x80x9d) containment in electronic systems. More particularly, the invention relates to the containment of EMI that is generated in and around an integrated circuit chip.
Digital electronic systems such as computers tend to radiate electromagnetic energy. Generally this radiated electromagnetic energy is unwanted because it may interfere with the operation of other electronic systems located near the radiating system. This phenomenon is known both as electromagnetic interference (xe2x80x9cEMIxe2x80x9d) and radio frequency interference (xe2x80x9cRFIxe2x80x9d). As used herein, the term EMI will refer both to EMI and to RFI. Regulations exist in the United States and other countries that specify legal maxima for EMI caused by electronic products. It is therefore important to design electronic products so that the electromagnetic energy generated within them is minimized or effectively contained.
High-speed digital integrated circuit chips such as microprocessors are particularly prominent generators of EMI. Integrated circuit chips of this type also generate a relatively large amount of heat energy, which energy must be removed from the chip or redistributed so that the chip will not overheat and fail.
A need therefore exists for a technique that will help to contain the EMI generated by an integrated circuit chip without impeding the removal of heat from the integrated circuit chip.
By way of further background, it is common to couple integrated circuit chips to printed circuit boards by means of a socket. A variety of socket types may be used with the same integrated circuit chip. Each of the various socket types may have different dimensions. In particular, each of the various socket types may have a different height. Thus, the distance between the top of a given integrated circuit chip and the surface of the printed circuit board will vary depending on which socket type is chosen for use.
An EMI gasket according to the invention exhibits enhanced compliance in the direction orthogonal to the plane of the circuit board on which a chip or chip-and-socket assembly is mounted. (As used herein, the term xe2x80x9cz axisxe2x80x9d will be synonymous with the direction just defined in the preceding sentence.) Because of the gasket""s enhanced compliance in the z axis, the gasket may be used with chips or chip-and-socket assemblies having a variety of heights. Embodiments of the invention can be defined from numerous points of view. For example:
In one aspect, a frame made from a sheet of metal has a planar portion with an opening formed therein. The opening is adapted to fit around a perimeter of an integrated circuit chip. The sheet of metal includes top and bottom planar surfaces. Top and bottom resilient conductive members are attached to the top and bottom planar surfaces, respectively.
In another aspect, a sheet metal frame defines an opening adapted to fit around a perimeter of an integrated circuit chip. The opening can be thought of as having an axis that passes orthogonally through it. The sheet metal of the frame includes top and bottom planar surfaces. Top and bottom resilient conductive members are attached to the top and bottom planar surfaces, respectively. The resilient conductive members are disposed such that a line can be drawn parallel to the axis of the opening and passing through both the top and the bottom resilient conductive members.
In another aspect, a sheet metal frame defines an opening adapted to fit around a perimeter of an integrated circuit chip. The sheet metal frame is folded to form top and bottom planar surfaces. Top and bottom resilient conductive members are attached to the top and bottom planar surfaces, respectively.
In another aspect, a sheet metal frame defines an opening adapted to fit around a perimeter of an integrated circuit chip. The sheet metal of the frame includes top and bottom planar surfaces. The top and bottom planar surfaces are not coplanar with one another, but they are coupled together by a conductive wall. Top and bottom resilient conductive members are attached to the top and bottom planar surfaces, respectively.
In a still further aspect, a sheet metal frame defines an opening adapted to fit around a perimeter of an integrated circuit chip. The sheet metal of the frame is folded to form top and bottom planar surfaces. Top and bottom resilient conductive members are attached to the top and bottom planar surfaces, respectively. Both the top and the bottom resilient conductive members are made with a resilient filler material covered with a conductive fabric.